1. Field of the Invention
The present invention relates to crystals of pharmaceutically acceptable salts of N-{2-chloro-4-[(6,7-dimethoxy-4-quinolyl)oxy]phenyl}-N′-(5-methyl-3-isoxazolyl)urea and a process for producing the same.
2. Related Art
In the field of research in the therapy of diseases such as tumors, diabetic retinopathy, chronic rheumatism, psoriasis, atherosclerosis, and Kaposi's sarcoma, a number of drugs have been used clinically through various approaches. Medical treatment with chemotherapeutics, however, has posed problems of side effects of drugs, individual differences in patients and the like. This has led to a demand for better drugs. Further, when QOL (quality of life) of patients is taken into consideration, an increase in diversification of dosage forms of drugs is demanded.
For example, in formulation into tablets, capsules, powders, granules, and suspensions for oral administration, or formulation into suppositories, tapes, and ointments for parenteral administration, original drugs should satisfy requirements for preparations as pharmaceuticals, that is, should have physicochemical properties that can realize prescription which satisfies prescribed quality and development of efficacy. Further, the original drug as a pharmaceutical should be produced by a process that can realize stable production of the original drug on a commercial scale and is suitable for mass production on a commercial scale.